After the end of WWII, in accordance with the Cairo Declaration and the Potsdam Proclamation, China recovered Taiwan, the Penghu Islands and other territories which Japan had occupied, meaning the Diaoyu Island and its affiliated islets were returned to China in terms of international law.

The Diaoyu Islands "nationalization" is just the latest provocation from Japan to have strongly reminded Chinese of the wartime past.

Sino-Japanese relations soured in the early 2000s with an interruption of the exchanges of high-level visits, due to then Japanese Prime Minister Junichiro Koizumi's repeated visits to the Yasukuni Shrine, which honors class-A WWII war criminals.

The bilateral ties began to mend after Koizumi's successor, Shinzo Abe, made positive gestures on historical issues.

In September 2010, a Chinese trawler collided with Japanese Coast Guard patrol boats near the Diaoyu Islands. The collision, and Japan's subsequent detention of the trawler captain, resulted in a major diplomatic dispute between the two nations.

Over the past four decades, Sino-Japan relations have made steady and constructive progress only when the two sides both stuck to the understanding of common ground they reached on the normalization of diplomatic ties in 1972 and in the Sino-Japanese Treaty of Peace and Friendship in 1978.

This understanding should continue to work on handling the issue of the Diaoyu Islands, as well as other barriers standing between the countries in the future.

The "purchase" of the Diaoyu Islands has stirred anger across China and triggered protests in several cities. The Japanese government should take note of mainstream Chinese public opinion, as voiced in those protests, and think twice about its illegal activities.

In a joint statement signed by Chinese President Hu Jintao and then Japanese Prime Minister Yasuo Fukuda in 2008, China and Japan agreed to "face history squarely, look forward to the future and make continuous joint efforts to open up new prospects in their strategic mutually beneficial relations."

Taking history as a mirror and looking into the future will continue to be the political prerequisite for ensuring stable and healthy development of Sino-Japan relations.